Download Genetics

Genetics
The study of heredity
Review Questions

What is DNA? What does it do for you?
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Where do you get your DNA from?
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Its your genetic information, sort of like a blueprint
Your mom and dad
How much do you get from each parent?
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50 %
Review Questions
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What is a Karyotype?
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A picture of a persons chromosomes paired up
and put in order.
How many pairs of chromosomes does a
human have?
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23 pairs including the sex chromosomes
Review Questions
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What are the two sex chromosomes?
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What sex chromosomes does a female
have?
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X&Y
XX
A male?
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XY
What is Genetics?

Genetics – The study of genes and how they
are passed from parents to offspring.
http://ghr.nlm.nih.gov/handbook/illustrations/autodominant.jpg
Vocabulary Continued:

Gene – A section of DNA that codes for a
specific trait or characteristic of an organism.
Ex. Hair Color Gene
http://www.virtua.org/ADAM/graphics/images/en/9344.jpg

Allele – A version of a gene. For example,
brown hair allele, black hair allele, & red hair
allele.
History of Genetics


Gregor Mendel:
Austrian Monk who carried out the first important
studies of heredity.

Mendel chose to use the pea plant in his
experiments.
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Pea plant was an excellent subject because Mendel
was able to pollinate the plants himself.
Mendel’s Experiment
Mendel’s work

Bred pea plants
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P = parental
raised seed & then
observed traits (F1)
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P
cross-pollinate
true breeding parents (P)

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Pollen transferred from white
flower to stigma of purple flower
F = filial
allowed offspring
to self-pollinate
& observed next
generation (F2)
anthers
removed
all purple flowers result
F1
self-pollinate
F2
Mendel collected data for 7 pea traits
Looking closer at Mendel’s work
P
F1
true-breeding
true-breeding
X
purple-flower peas
white-flower peas
100%
purple-flower peas
Where did
the white
flowers go?
100%
generation
(hybrids)
self-pollinate
F2
generation
75%
purple-flower peas
White
flowers came
back!
25%
white-flower peas
3:1
Genetics in humans


Genetics works on everything from bacteria
to humans.
Some examples of genes in humans would
be the genes for:
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Hair color
Eye color
Free or attached earlobes
Curly or strait hair
Etc.
How genes work Pt1

Each gene can have many different alleles.
For example, the free or attached earlobe
trait has two different alleles.
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One for free earlobes (E) One for attached (e)
How genes work Pt2

Every organism, in this case a human, has
two copies of each gene (one from the mom
and one from the dad).
+
=
How genes work Pt2

This means that you could have one copy of
the free earlobe allele and one copy of the
attached earlobe allele (Ee). Or two copies
of either allele (EE) or (ee).
How genes work Pt3

In this case, the person would have free
earlobes; because, some alleles are
dominant over others.
Ee =
Genes for beginners

Dominant – Represented by a capital letter,
this allele will cover up a recessive allele.

Recessive – Represented by a lower case
letter, this allele will only be visible if there is
no dominant allele present.
Practice:
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Brown eyes = B
Blue eyes = b
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Which one is dominant?
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Brown eyes
What color eyes would a person with BB
have?
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Brown
Practice continued
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Brown eyes = B
Blue eyes = b
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What color eyes would a Bb person have?
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Brown eyes
How about a bb person?
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Blue eyes
Genes for beginners
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When we talk about the alleles that are
involved and give examples like Bb, AA, ee
we are talking about the genotype of
something.

Genotype – The genes that a person or
organism has, represented by upper and
lower case letters. For example, a genotype
could be “Bb”.
Genes for beginners

When we talk about what characteristics we
will actually see. For example, brown eyes
or blue eyes we are talking about the
phenotype. (Think phenotype = physically see)
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Phenotype – The trait that you see physically.
For example, a phenotype could be brown
eyes.
Genes for beginners
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If an individual has two of the same type of
allele then we call that homozygous
(remember the prefix “homo” means “same”)

Homozygous – When an organism has two
of the same alleles. Example: bb
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Homozygous dominant = BB
Homozygous recessive = bb
Genes for beginners
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If an individual has two different alleles we
call them heterozygous. Remember the
prefix “hetero” means “different”
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Heterozygous – When an organism has two
different alleles. Example: Bb
Practice:
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Is Bb a genotype or a phenotype?
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Is this individual homozygous or heterozygous?
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Genotype
Heterozygous
If B stands for brown eyes and b stands for blue
eyes what color eyes would this person have?
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Brown eyes